This man is missing 90% of his brain yet lives a normal, healthy life

Scientists are baffled
about the case of a French man who lives a normal life despite
missing 90 percent of his brain.PBS/YouTube

A French man who lives a relatively normal, healthy life -
despite missing 90 percent of his brain - is causing scientists
to rethink what it is from a biological perspective that makes us
conscious.

Despite decades of research, our understanding of consciousness -
being aware of one's existence - is still pretty thin. We know that it's somehow
based in the brain, but then how can someone lose the majority of
their neurons and still be aware of themselves and their
surroundings?

The French man was 44 years old at the time the journal article
came out, and although his identity was kept confidential, the
researchers explained how he'd lived most of his life without
realising anything was wrong with him.

He only went to the doctor complaining of mild weakness in his
left leg, when brain scans revealed that his skull was mostly
filled with fluid, leaving just a thin outer layer of actual
brain tissue, with the internal part of his brain almost totally
eroded away.

Doctors think the majority of the man's brain was slowly
destroyed over the course of 30 years by the build-up of fluid in
the brain, a condition known as hydrocephalus. He'd been
diagnosed with it as an infant and treated with a stent, but it
was removed when he was 14 years old, and since then, the
majority of his brain seems to have been eroded.

But despite his minimal remaining brain tissue, the man wasn't
mentally disabled - he had a low IQ of 75, but was working as a
civil servant. He was also married with two children, and was
relatively healthy.

Not only did his case study cause scientists to question what it
takes to survive, it also challenges our understanding of
consciousness.

In the past, researchers have suggested that consciousness might
be linked to various specific brain regions - such as the
claustrum, a thin sheet of neurons running
between major brain regions, or the visual cortex.

But if those hypotheses were correct, then the French man
shouldn't be conscious, with the majority of his brain missing.

"Any theory of consciousness has to be able to explain why a
person like that, who's missing 90 percent of his neurons, still
exhibits normal behaviour," Axel Cleeremans, a cognitive
psychologist from the Université Libre de Bruxelles in Belgium,
told Quartz.

In other words, it's unlikely that one specific region on its own
is going to be responsible for consciousness. It's
unlikely that only one region is responsible for
consciousness.Allan
Ajifo/Flickr

Cleeremans has instead come up with a hypothesis that's based on
the brain learning consciousness over and over
again, rather than being born with it. Which means its location
can be flexible and learnt by different brain regions.

"Consciousness is the brain’s non-conceptual theory about itself,
gained through experience - that is learning, interacting with
itself, the world, and with other people," he explains.

"Cleeremans argues that in order to be aware, it’s necessary
not simply to know information, but to know that one knows
information. In other words, unlike a thermostat that simply
records temperature, conscious humans both know and care that
they know.

Cleeremans claims that the brain is continually and
unconsciously learning to re-describe its own activity to
itself, and these descriptions form the basis of conscious
experience."

But what does all that have to do with a man surviving with only
10 percent of his brain? According to Cleeremans, even though his
remaining brain was only tiny, the neurons left over were able to
still generate a theory about themselves, which means the man
remained conscious of his actions.

Our brains are truly flexible.Samba Tech

In itself, the concept isn't new - we're discovering more and
more each day just how flexible and adaptable our brains really are.
Just this week, scientists were able to trigger brain cells to
start growing again in order to restore vision in blind mice.

But it's a striking reminder of what our brains can learn to
achieve, even when they're incredibly damaged, and provides hope
that we might one day learn how to reverse some of the illnesses
that cause neurodegeneration.